When a motor is used in a limited installation space such as in a vehicle, an inverter that performs a driving control of the motor is integrated with a motor housing in order to reduce the installation space. In this case, a stray capacitance exists between the motor housing, and a pattern and a wire that are at the same potential as a connection point between upper and lower arms of the inverter. Meanwhile, in the pattern and the wire that are at the same potential as the connection point between the upper and lower arms of the inverter, the potential varies between a DC potential and 0 volt at a high speed. Therefore, when the motor housing is connected to a power-supply ground, a common-mode current flows to a power supply of the inverter and causes noise to occur in other devices connected to the same power system.
To prevent such noise from adversely affecting other devices, there is a common procedure to provide a noise filter on an AC side or a DC side of an inverter, thereby forming a shortcut path for returning a common-mode current to an inverter side to prevent the common-mode current from flowing out to a power supply.
Patent Literature 1 discloses a technique in which a power switching element and a smoothing capacitor that are fixed to an outer peripheral surface of a peripheral wall of a motor housing and a control circuit mounted on a printed circuit board or the like eventually fixed to the motor housing are wired and connected by a bus-bar built-in plate and outer frame part serving as a wiring part.
In addition, Patent Literature 2 discloses a technique in which a power module includes a wide-bandgap power semiconductor switching element, the power module and a power-module drive circuit are accommodated in separate housings, and the housing having the power module accommodated therein is fixed to a housing of a transmission, an engine, or a motor in order to cool the power module.